Signalling switch gear



Jan. 4, 1966 J. M. BENJAMINSEN ETAL 3,228,013

S IGNALLING SWITCH GEAR Original Filed Nov. 19, 1959 United StatesPatent 3,228,018 SIGNALLING SWITCH GEAR Joseph M. Benjaminsen andHenricus H. M. Hamelers, Beck, Netherlands, assignors to Stamicarbon N.V., Hcerlen, Netherlands Continuation of application Ser. No. 854,174,Nov. 19, 1959. This application Sept. 18, 1962, Ser. No. 224,392 Claimspriority, application Netherlands, Nov. 22, 1958,

4 Claims. ct. 340-256) This invention relates to a signalling circuitand more particularly to an improved circuit wherein a change in currentwithin an electrical system is effectively recognized and indicated.

The present application is a continuation of the pending United Statesapplication Serial No. 854,174 filed on Nov. 19, 1959, now abandoned.

in an electrical system, which for example may comprise a plurality ofelectric motors, measuring devices, etc., it has been the usual practiceto provide indicating devices for each piece of equipment in the form ofa visual indicator by which changes in the state of operation of theequipment are shown. In addition to these visual signals there is oftenprovided an audio indicator to supplement the visual devices. Systemsutilizing this combined signalling arrangement in the past haveinhcrently made the operation of the audio indicator dependent on properoperation of the visual devices when the audio and visual members wereelectrically interconnected. To avoid the reliability problems whichhave arisen due to faulty operation of the visual indicators in priorart arrangements, other systems have employed audio and visualindicators entirely independent of one another with the resultantdisadvantage of increased equipment costs.

These shortcomings have been overcome in the present invention by animproved signalling circuit which functions on changes in current in theelectrical system to actuate the audio indicator.

An object of the invention is to provide an electrically interconnectedsignalling circuit having indicators for each piece of equipment in thesystem as well as supplemental indicating means operativeiy independentof the individual indicators.

A further object is to provide an improved signalling circuit withoutthe necessity of employing costly independent circuit components.

The foregoing objects are accomplished by electrically by-passing theindividual indicator means associated with each piece of equipment bytransient responsive components which couple the sudden changes incurrent of the equipment to circuitry which is responsive only totransients to energize the supplemental indicator.

Other objects and advantages will be apparent from the followingdescription of an illustrative embodiment of the invention, pointed outparticularly in the appended claims, when the foregoing are taken inconjunction with the accompanying drawing in which one embodiment of theinvention is shown.

Referring to the drawing, an exemplary electrical system is shown. Thissystem includes several lines which, in the illustrative embodiment,comprise a pair of motors 1, and a measuring instrument 18. Thesignalling circuit, illustrated as being associated with a signallingpanel 15, is connected to a voltage source through relay controlledswitches operated by the equipment, the motors 1 and measuringinstrument 18. Non-capacitive impcdances are joined in series with eachof the several lines. These include individual primary indicators, suchas lamps 2, associated with each piece of equipment. In parallel witheach of the lamps is a condenser 16. With all of the equipmentcontrolled switches closed, all of the lamp circuits are in parallelwith one another and in series with an impedance 17 across the supply.

A change-over switch 3 is shown associated with one of the motors 1.This switch is employed when the motor is switched off intentionally.However, this switch is not an essential part of the invention and isincluded only to illustrate an incidental feature of the arrangement.

in parallel with impedance 17 between two points in the system is ashunt line comprising a series combination of a condenser 20 and theprimary winding of a peaking transformer 4. The secondary winding isconnected to an output device which includes an amplifying device, inthis case a thyratron tube 5, su h that any signal on this winding issupplied to tube 5 as an input. A positive direct current voltage supplyis normally connected to the plate of tube 5 through a relay winding 6and the normally closed contacts 7 operatively associated with a relaywinding 8. The relay contacts controlled by winding 6 are normally opencontacts 9 and 11. When closed, contacts 9 complete a circuit throughwinding 8 from the positive side of the direct voltage source to thenegative side. Contacts 11 operate concurrently with contacts 9 toconnect this negative reference to the input grid of tube 5. Relaywinding 8 has associated with it not only normally closed contacts 7,but also normally open contacts 10 and 12. These contacts operateconcurrently such that when the relay operates, contacts 7 open andcontacts 10 and 12 close. Closure of contacts 12 completes a circuitthrough an indicator, in this case an audio device 13, between thepositive and negative voltage references. Simultaneously, contacts 10ciose to connect a circuit comprising winding 8 and a mechanical switch14 in parallel with the audio device 13.

Although an alternating source is shown, either an alternating or adirect voltage source may be utilized to energize the lamps 2 and theimpedance 17. If a directcurrent source is employed, impedance 17comprises a resistor which offers a very low impedance to teady-statecurrent through resistor 17, as opposed to that of the condenser 20 andprimary winding combination in parallel therewith, whereas rapidlychanging current intensities encounter very low relative impedancethrough the series arrangement of the condenser 20 and the transformerprimary as compared with resistor 17.

The same type of relative impedance relationship is desired between theimpedance 17 and the condenserprimary winding circuit in paralleltherewith when an alternating source is employed. This may be achievedby utilizing a filter circuit as impedance 17, this filter offering highimpedance to transients and low impedance to steady-state conditions.

Transformer 4 is a peaking transformer, i.e., a known type oftransformer which, by the special construction of its magnetic circuit,is suited to transform steep peaks, and responds poorly to "slowly"changing or steady state currents. By employing such a transformer,primary currents of varying strengths but with steep slopes can produceappreciable secondary signals.

Since the peaking transformer does produce an appreciable output inspite of the fact that a low amplitude signal is applied to the primarywinding thereof, it is necessary to connect the secondary winding to adevice which operates only above a certain threshold value in order toinsure that the supplemental indicating device 13 will not be energizeddue to stray disturbances sensed by the peaklng transformer.Accordingly, in this embodiment a thyratron is employed. However, otherdevices such as a cold cathode tube, a transducer, etc. may also beutilized.

Although the primary indicators 2 are set forth as lamps and thesupplemental indicator 13 is an audio device, it will be understood thatsuch an arrangement is for purpose of illustration only and otherindicating devices may easily be substituted therefore within the scopeof the invention.

With the structural features of the signalling system set forth, atypical cycle of operation will now be described. A change in theelements of the electrical system, motors 1 and measuring equipment 18,results in the closing of associated contacts in the signalling circuitto connect the appropriate indicating devices 2 to the supply voltage.The initial current surge in the signalling circuit is a transient whichis shunted around lamp 2 by the condenser 16 and which by-passesimpedance 17 which offers a relatively high impedance to transients. Inbypassing impedance 17, the primary winding of peaking transformer 4 isenergized to produce an appreciable output at its secondary. This signalis applied to the thyratron to cause conduction thereof. The change incurrent in the plate circuit of tube 5 energizes relay winding 6,closing contacts 9 and 11. With a negative voltage now applied to thethyratron grid through contacts 11, the tube will be cut off. Theclosing of contacts 9 results in completing a circuit through winding 8between the positive and negative references. The initial surge ofcurrent in this circuit energizes relay winding 8 to open contacts 7while simultaneously closing contacts 10 and 12. The opening of contacts7 cuts off relay winding 6 from the plate circuit of tube 5 therebyde-energizing the relay and allowing contacts 9 and 11 to open. Relaywinding 8 accordingly is connected to the negative reference throughcontacts 10 and 14. Since contacts 12 are closed, indicator 13 isenergized. When it is desired to terminate the operation of device 13,switch 14 is opened to deenergize relay winding 8. This opens contacts10 and 12 and closes contacts 7. Indicator 13 is thereby de-energizedand the circuit is in its initial condition ready to respond to the nextsignalling transient sensed by the peaking transformer 4.

It should be particularly noted that the operation just described isdependent only on the transient current caused by the change incondition of the elements of the electrical system being monitored. Theenergization of indicator 13 does not require the operation of anindicator 2 even though these two types of indicators are present in thesame signalling circuit. Thus, the signalling circuit is operative eventhough the primary indicators 2 may be defective During the steady-statecondition when the signalling circuit is energized, the peakingtransformer is inoperative since at this time its primary winding iseffectively bypassed by the impedance 17. Accordingly, indicator 13 isoperative only if switch 14 has not been opened. After the initialtransient, the steady-state current effectively by-passes condenser 16through indicator 2. Thus, the appropriate indicator 2 becomes theprincipal signalling means to indicate that an element of the electricalsystem has changed its condition.

The particular circuitry arrangement shown is only an example of thesignalling circuit in which the inventive features of this disclosuremay be utilized. It will be readily apparent to one skilled in the artthat certain modifications may be made to the arrangement within thespirit of the invention as defined by the appended claims.

What is claimed is:

1. A signalling circuit to detect sudden transient electrical currentswithin an electrical system having a plurality of lines therein, saidtransient currents being created by abrupt changes of steady-statecurrents in said lines, comprising: a transformer having a primary andsecondary winding, a shunt line including said primary wind ing coupledacross two points of said system, an impedance connected between saidtwo points and joined in series with said plurality of lines, saidimpedance being characterized by having a low value with respect to saidshunt line during steady-state operation and a high value with respectto the shunt line during transient periods within said system; at leastone output device coupled to said secondary winding; non-capacitiveimpedances in series with each of said plurality of lines, andcapacitive means in parallel with said non-capacitive impedances forproviding a path for transient currents around said noncapacitiveimpedances and through said primary winding to thereby energize saidsecondary winding and said output device.

2. A signalling circuit as set forth in claim 1, said noncapactiveimpedances including primary indicating means and said output devicecomprising supplemental indicating means.

3. A signalling circuit as set forth in claim 2 wherein said transformeris a peaking transformer.

4. A signalling circuit as set forth in claim 2 wherein said transformeris a peaking transformer and said shunt line includes a condenser inseries with said primary windmg.

References Cited by the Examiner UNITED STATES PATENTS 2,329,090 9/ 1943Smith ct a1. 328-74 X 2,724,107 11/1955 Born 340-248 2,800,645 7/1957Koch 3402l3 2,832,068 4/1958 Warren 340-213 2,994,073 7/1961 Pelovitz340248 X NEIL C. READ, Primary Examiner.

1. A SIGNALLING CIRCUIT TO DETECT SUDDEN TRANSIENT ELECTRICAL CURRENTSWITHIN AN ELECTRICAL SYSTEM HAVING A PLURALITY OF LINES THEREIN, SAIDTRANSIENT CURRENTS BEING CREATED BY ABRUPT CHANGES OF STEADY-STATECURRENTS IN SAID LINES, COMPRISING: A TRANSFORMER HAVING A PRIMARY ANDSECONDARY WINDING, A SHUNT LINE INCLUDING SAID PRIMARY WINDING COUPLEDACROSS TWO POINTS OF SAID SYSTEM, AN IMPEDANCE CONNECTED BETWEEN SAIDTWO POINTS AND JOINED IN SERIES WITH SAID PLURALITY OF LINES, SAIDIMPEDANCE BEING CHARACTERIZED BY HAVING A LOW VALUE WITH RESPECT TO SAIDSHUNT LINE DURING STEADY-STATE OPERATION AND A HIGH VALUE WITH RESPECTTO THE SHUNT LINE DURING TRANSIENT PERIODS WITHIN SAID SYSTEM; AT LEASTONE OUTPUT DEVICE COUPLED TO SAID SECONDARY WINDING; NON-CAPACTIVEIMPEDANCES IN SERIES WITH EACH OF SAID PLURALITY OF LINES, ANDCAPACITIVE MEANS IN PARALLEL WITH SAID NON-CAPACITIVE IMPEDANCES FORPROVIDING A PATH FOR TRANSIENT CURRENTS AROUND SAID NONCAPACITIVEIMPEDANCES AND THROUGH SAID PRIMARY WINDING TO THEREBY ENERGIZE SAIDSECONDARY WINDING AND SAID OUTPUT DEVICE.